When one or more of the cylinder walls of a particular block is damaged or its measured dimensions are outside those considered acceptable after normal machining, it may seem easier and more cost effective to simply use another block as opposed to salvaging the existing unit. While that can absolutely be true in instances where a Pontiac's factory-installed block is already missing, or in race applications where correctness isn't a concern, there are times when owners will go to great lengths to salvage a numbers-matching block to maintain originality, and ultimately, maximum vehicle value.
Jon Carbonneau of Beatrice, Nebraska, purchased a '69 LeMans equipped with the desirable 350 H.O. engine option a couple of years ago. It seems the Pontiac had been sitting since 1990 and someone had stolen its original Quadrajet carburetor. In an attempt at preservation, the previous owner simply covered the naked intake manifold with a sleeping bag, and the car sat in that state for several years.
The sleeping bag stuffing was an invitation for small rodents and the 350 H.O. quickly became a condominium for mice with every internal crevice of the induction system occupied by multiple families of them. The byproducts of their inhabitance took its toll on the 350's internals, and many of the exposed surfaces corroded badly over time.
The "XU" stamping indicates...
The "XU" stamping indicates that this particular engine is a 350 H.O. from a '69 A-body. Featuring large-valve No. 48 cylinder heads, a No. 067 camshaft, and a four-barrel carburetor, the 350 H.O. was a respectable performer, rated at 330hp that model year. The fact that only 2,800 XU-code engines were assembled is reason enough to attempt to salvage this LeMans' original block during its restoration.
When Jon took possession of the LeMans, he bought it with the intention of restoring the unique Pontiac, and was fully aware that a complete engine rebuild was in order. As he began the teardown, however, he discovered that at least two pistons were frozen in their respective cylinders. Expecting the worst, he enlisted the experience of Chuck Willard of Willard Auto Machine in Omaha, Nebraska, to assess the damage to his LeMans' numbers-matching engine.
After a thorough cleaning and inspection, Willard determined that the 66,000-mile engine was actually in excellent shape, but that the surface walls of two cylinders were so deeply corroded that they'd need to be machined well beyond a comfortable amount to reach unaffected iron for maximum piston seal. Chuck then explained to Jon that the installation of cylinder sleeves was the only way the original 350 block could be reused, and that it's widely accepted as a permanent repair with proven results.
A cylinder sleeve is simply a cast-alloy liner that's commonly used to restore the contact surface of a cylinder wall that has been damaged or corroded, or excessively worn or machined. It's used to recreate the ideal conditions to guide a piston and contain combustion within a block. Many modern production engines with a cast-aluminum block, such as those in the LS-series for example, feature cast-alloy liners directly from the factory. Myriad aftermarket companies offer cylinder sleeves in virtually any shape and size, and their simple installation makes them a popular and cost effective method of repairing a block.
HPP was on hand to document the installation process, which is applicable to most any Pontiac block that a competent machinist has deemed as a candidate for cylinder sleeving. While not all blocks are salvageable, and it might sometimes be easier and more cost effective to simply start with another, nothing changes the fact that cylinder sleeving is a permanent repair that can be used to restore the functionality of a Pontiac's original, numbers-matching block! Read on to see how it's done.
Typical cylinder-wall wear...
Typical cylinder-wall wear associated with normal operation usually results from the friction that's generated during piston travel and the combustion process. Actual wall damage can occur when foreign matter enters the oil, scoring the surface. In either instance, an overbore of at least 0.030 inch, and possibly as much as 0.060-inch, will generally remove enough material from the cylinder-wall surface to restore functionality without compromising a cylinder's structural integrity or affecting its ability to transfer heat. Corrosion this severe requires removing much more material, leaving less of the original wall than what's considered safe for a Pontiac V-8.
LA Sleeve Company in Santa...
LA Sleeve Company in Santa Fe Springs, California, produces cylinder sleeves in a wide range of diameters and wall thicknesses for use in any internal-combustion engine block. Cylinder sleeves act and function just as if they were the block's original cylinder wall once installed, and can be re-machined during future rebuilds. Constructed of cast-iron alloy that's centrifugally spun, LA Sleeve Company offers custom sleeves for unique applications, while off-the-shelf sleeves that fit a Pontiac V-8 start around $25. (Photo supplied by the manufacturer.)
Chuck Willard of Willard Auto...
Chuck Willard of Willard Auto Machine (WAM) in Omaha, Nebraska, determined that the corrosion was essentially cosmetic and that 0.090-inch wall sleeves were required to repair the affected cylinders of this particular 350. A 0.125-inch-wall sleeve would be a better choice if a severe crack was present. Willard mounts the block to his vertical boring mill, squares it up, and properly locates it to precisely machine the cylinder.